Balanced drive mechanism for a



Oct. 22, 1963 fi o fi/JPLAC'EMEN C. R. CANFIELD. JR

BALANCED DRIVE MECHANISM FOR A FUEL INJECTION PUMP Filed June 23. 1960 [aver-Liar: Carl J5. C agleld, Jr.

\ L ffil IP -H in! T] United States Patent Filed June 23, 1960, Ser. No. 38,214 Claims. (Cl. 103-457) This invention relates to a dynamically balanced drive mechanism for a fuel injection pump.

in the design of an acceptable fuel injection system it is desirable to adapt the system to existing engines with a minimum of structural changes to the engines. The location and method of operation of some of the components of the fuel injection system often places some undue loads on the existing elements of the engine.

In a timed fuel injection system, it is necessary that the delivery of metered charges of fuel be accurately correlated with the opening of the inlet valves of the engine. To ensure that the timing is accurate, it is preferable to drive the fuel injection pump at a fixed ratio with respect to the engine cam shaft. For this purpose a drive mechanism has been provided that is driven from the engine distributor shaft which, in turn, is driven by the engine cam shaft.

The power required to drive the fuel injection pump is significant and places a load on the distributor shaft and cam shaft in addition to that for which they were originally designed.

The fuel injection pump with which the improved drive mechanism is intended to be used includes a plunger that is reeiproeated for pumping fuel and rotated for distributing charges of fuel to the engine cylinders. The pump also includes a return spring for returning the pumping plunger. The load due to the fuel injection pump is pulsating in character and tends to reflect undesirable pulsations back to the distributor shaft and engine cam shaft. The drive mechanism of the present invention has been designed specifically to minimize the pulsations due to the action of the reciprocating plunger and to even out the load on the engine distributor shaft and cam shaft.

it is, therefore, an object of the present invention to provide an improved drive mechanism for a fuel injection pump having a reciprocating plunger, the mechanism being effective to minimize pulsations or oscillations in the drive train due to the reciprocation of the pumping plunger.

it is a more particular object to provide a drive mechanism for a fuel injection pump having a rotatable and reciprocable plunger and a circular face cam in contact with a plurality of rollers for reciprocating the plunger. and additional cam means mounted in such a manner that its phase relationship and torsional load with respect to the first cam can be adjusted so as to minimize pulsations in the drive train for driving the pumping plunger.

The invention consists of the novel constructions, arrangemcnts, and devices to be hereinafter described and claimed for carrying out the above-stated objects and such other objects as will appear from the following description of a preferred form of the invention, illustrated with reference to the accompanying drawings, wherein:

P10. 1 is a sectional view of the improved drive mechanism of the present invention for a fuel injection pump;

HO. 2 is a vector diagram illustrating the forces developed in the drive mechanism of FIG. I; and

FIG. 3 is a modification that may be incorporated into the drive mechanism of FIG. I.

Like characters of reference designate like parts in the several views.

Referring to FIG. l, there is illustrated the improved drive mechanism of the present invention designated gen- 3,107,631 Patented Oct. 22, 1963 erally by the numeral 10. Also illustrated in the figure are an electrical ignition distributor 11 for the engine, a distributor shaft 12 for driving the distributor 11 and drive mechanism 10, and an engine cam shaft 13 for driving the distributor shaft 12. The distributor shaft 12 carries a spur gear 14 on one end thereof in mesh with a driving gear 15 on the cam shaft 13. The drive mechanism 10 is connected to drive a fuel injection pump 16 having a pumping plunger 17.

The drive mechanism 10 comprises a casing 20, a drive shaft 21 rotatably mounted in the casing 20, a drive pulley 22 keyed to the distributor shaft 12. a driven pulley 23 keyed to the drive shaft 21. a cogged timing belt 24 interconnecting the pulleys 2Land 23, a drive cam 25 attached to the pumping plunger 17, a first set of rollers 26 in contact with the cam 25, a compensating cam 27 mounted on the drive shaft 21, and a second set of drive rollers 28 in contact with the cam 27. The drive shaft 21 is formed with a driving tang 29 on one end thereof which engages a transverse slot 30 formed in drive cam 25. The cam 25 also carries a transverse drive pin 31 which extends through a transverse slot formed in one end of the pumping plunger 17. The pumping plunger 17 carries a spring retaining collar 32 and a spring 33 forces the pumping plunger 17 into contact with the drive cam 25 and, in turn. forces the cam 25 into contact with the rollers 26. The cam 25 is formed with a plurality of lobes or undulations 34 on one face thereof which are in contact with the rollers 26 and are effective to impart the reciproeative motion to the pumping plunger 17 as it rotates. The rollers 26 are rotatably mounted on pins 35 which are fixedly mounted within the casing 20 at right angles to the axis of the drive shaft 21.

The cam 27, for purposes of illustration, may be identical to the drive cam 25 and is keyed to the drive shaft 21 by means of a transverse pin 36. The cam 27 is formed with a plurality of lobes or undulations 37 on one face thereof which are in contact with the rollers 28. The rollers 28 are rotatably mounted on pins 38 which are fixedly mounted within the casing 20 at right angles to the axis of the drive shaft 21 and also at right angles to the axes of the pins 35. The cam 27 is forced into contact with the rollers 28 by a spring 39 which, for purposes of illustration. may also be identical to the spring 33. The spring 39 is retained under compression within a retaining cup 40 which is fixedly mounted within the casing 20. Thrust bearings 41 and 42 are provided within the casing 20 for each of the springs 33 and 39, respectively.

in operation. the drive mechanism 10 functions as follows:

The engine cam shaft 13 drives the distributor shaft 12 which, in turn, drives the distributor 11 and pulley 22. The pulley 22 drives the timing belt 24 which, in turn. drives the pulley 23 and the drive shaft 21. The drive shaft 21 rotates at a 1:1 ratio with respect to the cam shaft 13 and the tang 29 drives the cam 25 and pumping plunger 17 at the same ratio. As the drive cam 25 rotates, the rollers 26 in contact with the undulations 34 force the pumping plunger 17 upward during a pumping stroke. During the return or fill stroke, the rollers 26 roll downhill on one of the undulations 34 and the spring 33 forces the plunger 17 and cam 25 downwardly. The pumping and fill strokes are repeated for delivering fuel in sequence to each of the engine cylinders.

Referring to FIG. 2, the cam surfaces 34 and 37 of the cams 25 and 27, respectively. are exaggerated for purposes of illustration. The rollers 26 and 28 are also shown displaced from their actual physical position, but their relationship on the time axis corresponds to that of the embodiment of FIG. 1. The springs 33 and 39, respectively, force the earns 25 and 27 into contact with the rollers 26 and 28, and vector diagrams are illustrated to describe the reaction force of the rollers against the cams for various positions in a pumping cycle. At time 1 the roller 26 is in contact with the cam surface 34 at a trough designated by the numeral 50. In this position the drive earn and pumping plunger 27 are at a lowermost position of a downstroke. At the same time the roller 28 is in contact with the cam surface 37 at a point 51 corresponding to a peak on the cam surface. Since the rollers 26 and 28 are free to roll. the reaction force exerted by each is normal to the respective cam surfaces and at time t, is parallel to the axis of the drive shaft 21. The forces exerted by the rollers 26 and 28 are illustrated by vectors 52 and SJ, respectively. At this particular instant of time, there is no force transverse to the axis of the drive shaft 2|.

After a time r,, the drive shaft 21 has rotated from the position shown at time r,. and the roller 26 is at a point 54 corresponding to a peak on the cam surface 54. Similarly. the roller 28 is at a point 55 corresponding to a trough on the cam surface 37. At this time, the reaction force of the rollers 26 and 28 against the respective cams is again parallel to the axis of the drive shaft 2l. The force exerted by the rollers 26 and 28 st time I, is illustrated by the vectors 56 and 57, respectively.

At some intermediate time, such as time 1,. the roller 26 is in contact with the cam surface 24 at a point 58. The force exerted by the roller 26 is normal to the surface and is illustrated by the vector 59. The vector 59 can be resolved into a horizontal component 60 and a vertical component I. Similarly at time I, the roller 28 is in contact with the cam surface J7 at a point 62 and the force exerted by the roller against the cam 27 is illustrated by the vector 5. The vector 5 may also be resolved into a horizontal component 4 and a vertical component 65. The vertical components I and 65 may be neglected for the present discussion. The horizontal component 60 is transverse to the axis of rotation of the drive shaft 21 and exerts a torque on it. If the point of contact between the roller 26 and cam surface 54 is s distance R from the axis of the drive shaft 2|. the torque will be equal to the product of the force F, represented by the vector 0 times the radius It. This amount of torque must be supplied by shaft 2! at this instant of time to drive the pumping plunger 11 during its compression stroke. By the time r,, this torque drops to zero.

At time n. the roller 26 is in contact with the cam surface at a point 6 and exerts a force represented by the vector 67. The vector 67 can be resolved into a horizontal component 6| and a vertical component 6. The horizontal force I may be represented by F. sad the torque tending to turn the drive shaft 2! is equal to the product of FgXR- it should be noted that the direction of F, is opposite from that of F consequently. the torque tending to turn the shaft 21 is in the opposite direction. This oscillation of turning torque during each pumping cycle from one direction to the other would be reflected back through the timing belt 24 and pulley 22 to the distributor shaft [2 and cam shaft I). This fluctuating driving requirement of the pump 16 would place an undue load on the distributor shaft 12 and cam shaft Ll.

The earn 27, roller 22 and spring 3, are provided to compensate for these fluctuations in driving torque. At time 1,, roller 28 exerts a force against the cam 21 represented by the vector 0 and a horizontal component 64 may be a force of magnitude F,. The force F, is opposite in direction to that of P, and the torque exerted on shaft 2! is equal to 1-,xR. This torque exerted on the drive shaft 2|, therefore, tends to overcome the torque of F, xR and tends to assist the shaft 2t in driving the plunger 17 during its compression stroke. Similarly, at time t the roller 28 exerts a force represented by the vector 70 which may be resolved into a horizontal component 71 and a vertical component 72. The magnitude of the force 7l may be P. and the torque exerted on the drive shaft 21 is equal to F xR. At this instant of time, the force of F is in the opposite direction from the force F, and tends to balance the torque exerted by F, on the drive shaft 21.

The operation of the drive mechanism 10 may be summarized by noting that the pumping plunger 17 and the spring 53 absorb energy from the drive shaft 21 durtng the pumping stroke, and return energy to the shaft 21 on the fill stroke. The operation of the cam 27 and spring 39 is substantially out of phase with that of the cam 25, and the spring 39 absorbs energy from the drive shaft 21 during the filling stroke of the plunger 17 and returns energy to the drive shaft 2| during the pumping or compression stroke. The exact phase relationship of cam 27 with respect to earn 25 and the spring rate of spring 39 may be predetermined so as to most effectively cancel the torsional vibrations in the drive train.

The oscillating load of the two cams, therefore. is effectively cancelled and the load on the cam shaft 13 is fairly uniform. There may,be some slight fluctuation still present due to the fact that the resulting optimum phase relationship between the cams is not exactly 180 and the compression of the springs 53 and 39 are not 7 exactly the same at every instant of time.

Referring to H0. 3, there is illustrated a modification of the drive mechanism [0 in which the face cam 27 has been replaced by a cylindrical cam having an undulating cam surface 8| on its periphery. The roller 28 is replaced by a plurality of ball dctents 82 and the spring 39 is replaced by a plurality of springs 83, each acting against one of the balls 82. The cam 80 may be keyed to the shaft 2! or, if desired, the cam surface 81 may be formed on the outer periphery of the drive cam 25. In either configuration, the springs I5 are effective to absorb energy from the shaft 2i for part of each cycle and to return energy to the shaft 2t for the remainder of the cycle substantially out of phase with the drive cam 25 and spring 33. The combined action of the springs 85 is effective to cancel out the action of the spring 33.

There has been provided by this invention, an improved drive mechanism for a fuel injection pump having a reciprocating plunger, the mechanism being effective to compensate for the pulsations produced in driving the pumping plunger. The provision of the present mechanism tends to smooth out the driving load for the fuel in- )ectlon pump and thereby permits the pump to be driven without undue load on the distributor shaft or cam shaft of the engine.

it is contemplated that the improved drive mechanism can be driven by a timing belt connected directly to the engine carn shaft, rather than to the distributor shaft. The principles described for balancing the load on the cam shaft would still be applicable.

ft is to be understood that the invention is not to be limited to the specific constructions and arrangements shown and described. except only insofar as the claims may be so limited. as it will be understood to those skilled in the art that changes may be made without departing from the principles of the invention.

I claim:

l. in a drive mechanism for a fuel injection pump having s rotatable and a reclprocatlve plunger, the comblnation of s rotatable drive shaft connected to rotate said plunger, s first set of rollers fixedly mounted within said pump, s first circular face cam attached to one end of said pumping plunger and contacting said rollers for reciprocating the plunger as it rotates, s first spring connected to oppose axial displacement of said plunger in one direction and effective to move the plunger in the opposite direction, a second set of rollers also fixedly mounted within said pump, a second circular face cam mounted on said drive shaft and contacting said rollers, and a second spring acting against said second cam and tending to oppose axial displacement of said second cam as it rotates, said second cam being mounted in a relationship that is substantially out of phase with said first cam whereby one of said springs is being compressed while the other is being released so that the driving load on said drive shaft is substantially balanced.

2. ln a fuel injection pump adapted to supply metered charges of fuel to an internal combustion engine having a cam shaft and a distributor shaft driven by the cam shaft. the combination of a pumping plunger rotatably and reciprocatively mounted within said pump, cam means attached to said pumping plunger for reciprocating it as it rotates. a drive shaft rotatably mounted within said pump and connected to rotate said pumping plunger for distributing charges of fuel to the engine. timed driving means interconnecting said drive shaft with said distributor shaft for driving the pumping plunger at some fixed ratio with respect to said cam shaft. and additional earn means also mounted within said pump to act on said drive shaft and adapted to exert a torque on said drive shaft substantially out of phase with said first named cam means so as to balance the driving load on said distributor shaft.

3. in a fuel injection pump having a rotating and reciprocating plunger and adapted to supply charges of fuel to an internal combustion engine having a cam shaft and a distributor shaft driven by the cam shaft. the combination of a rotatable drive shaft mounted within said pump and adapted to rotate said plunger for distributing charges of fuel to the engine. driving means including a timing belt interconnecting said drive shaft with said distributor shaft. cam means including a first set of rollers mounted within the pump and a circular face cam contacting said rollers and adapted to reciprocate said plunger as it rotates. a first spring attached to said pumping plunger and adapted to maintain said cam in contact with said rollers. and second cam means including a second set of rollers. a second face cam connected to be driven by said drive shaft and a second spring effec ive to maintain said second cam in contact w th said toilet. said second cam means being mounted in a relationship substantially out of phase with said first cam means whereby one of said sprin s is being compressed while the other is being rele sed so that the driving load to reciproeation of said plunger is substantially balanced.

4. in a drive mechanism for a fuel injection pump having a ro stable and a reciprocative plunger and adapted to apply metered charges of fuel to an internal combustion engine having a cam shaft and a distributor shaft dt len by the cam shaft. the combination of s casing to med with a longitudinal bore for receiving the pumnng plunger. a drive shaft rotatably mounted within said casing and adapted to rotate said pumping plunger for distributing charges of fuel to the engine. a timing but interconnecting said drive shaft with said distributor hall for rotating the pumping plunger at a fised speed atio with respect to the engine cam shaft. a first set of rollers mounted within said casing with their ases at right angles to the axis of said drive shaft, a circular face cam attached to one end of said pumping plunger and adapted to reciprocate said plunger as it rotates. a first spring disposed under compression within said casing and adapted to oppose longitudinal movement of said plunger and to maintain said face cam in contact with said rollers. a second set of rollers also mounted within said casing with their axes at right angles to the axis of the drive shaft, a second circular face cam on said drive shaft and contacting said rollers. and a second spring disposed under compression within said casing and acting to force said second cam into contact with said second rollers. said second cam being mounted on said drive shaft in a relationship that is substantially out of phase with said first cam whereby one of said springs is being compressed while the other is being released so that the driving load of said pump is substantially balanced and oscillations due to reciprocation of the pumping plunger are sup pressed.

5. in a fuel injection pump adapted to supply charges of fuel to an internal combustion engine having a cam shaft and a distributor shaft driven by the cam shaft, the combination of a casing formed with a longitudinal cylindrical bore, a pumping plunger rotatably and reciprocably disposed within said bore. a drive shaft rotatably mounted within said casing and adapted to rotate said plunger for distributing the fuel charges to the engine. timed driving tncans interconnecting said drive means with said distributor shaft for rotating the pumping plunger at some fixed ratio with respect to said cam shaft, cam means for reciprocating said plunger as it rotates including a plurality of rollers mounted within said casing and a circular face cam attached to one end of said pumping plunger contacting said rollers. spring means for maintaining said cam in contact with said rollers. and additional cam means mounted within said casing in a relationship substantially out of phase with said circular face cam for thereby balancing the load'of the pumping plunger, said last-named means including a cylindrical cam formed with a contoured cam surface on its outer periphery and connccted to be driven by said drive shaft and a plurality of spring-loaded ball dctents in contact with said cam surface whereby said spring means is being compressed while said detcnts are being released and vice versa.

6. in a fuel injection pump adapted to supply metered charges of fuel to an internal combustion engine having a cam shaft. the combination of a pumping plunger rotatably and reciprocatively mounted within said pump. cam means attached to said pumping plunger for reciprocating it as it rotates. a drive shaft rotatabiy mounted within said pump and connected to rotate said pumping plunger for distributing the fuel charges in time to the engine. timed driving means interconnecting said drive shaft with said cam shaft for driving the pumping plunger at some fixed ratio with respect to said cam shaft. and additional cam means also mounted within said pump to act on said drive shaft and adapted to absorb energy from said drive shaft during a portion of each rotation and return energy to said drive shaft during another portion of each rotation so as to balance the driving load on said drive shaft.

7. in a fuel injection pump having a rotating and reciprocating plunger and adapted to supply charges of fuel to an internal combustion engine having a cam shaft. the combination of a rotatable drive shaft mounted within said pump and adapted to rotate said plunger for distributing the fuel charges to the engine, driving means including a timing belt interconnecting said drive shaft with said cam shaft. earn means including a first set of rollers mounted within the pump and a circular face cam contacting said rollers and adapted to reciprocate said plunger as it rotates. a first spring attached to said pumping plunger and adapted to maintain said cam in contact with said rollers. and second cam means including a sec- 0nd set of rollers. a second face cam connected to be driven by said drive shaft and a second spring effective to maintain said second cam in contact with said rollers. said second cam means being mounted in a relationship substantially out of phase with said first cam means whereby one of said springs is being compressed while the other is being released so that the driving load due to reciprocation of said plunger is substantially balanced.

8. in a fuel injection pump having a rotating and reciprocating plunger for supplying charges of fuel to an internal combustion engine the combination comprising: a rotatable drive shaft mounted within said pump and attached to rotate said plunger: a first cam means connectcd to the plunger and said drive shaft for effecting reciprocation of said plunger as said drive shaft is rotated; and a second cam means connected to said drive shaft and rotatable therewith. said second cam means being positioned in a substantially out of phase relationship with said first cam means to thereby effect a balancing of torque load on said drive shaft.

9. in a fuel injection pump having a rotatable and reciprocative plunger. the combination comprising: a. rotatable drive shalt for rotating said plunger, a first set of rollers mounted within said pump, first cam means attached to one end of said pumping plunger and contacting said rollers lor reciprocating the plunger as it rotates. first spring means connected to said first cam means to oppose axial displacement of said plunger in one direction and eliectlve to move the plunger in the opposite direction. a second set ol rollers mounted within said pump, second cam means connected to said drive shalt and associated with said second set ol rollers, and second spring means associated with said second cam means, said second cam means being mounted in a relationship that is substantially out ol phase with said first cam means to thereby ellect a balancing ol the torque load on said drive shall as the latter is rotated.

10. in a luel injection pump having a rotating and reciprocating plunger lor supplying charges ol luei to an internal combustion engine the combination comprising: a rotatable drive shalt mounted within said pump and attached to rotate with said plunger; a first cam means connected to the plunger and said drive shalt lor effecting reciprocation of said plunger as said drive shaft is rotated; a second cam means connected to said drive shaft and rotatable therewith; spring biasing means associated respectively with each of said cam means; said first and second cam means and the spring means respectively associated therewith being positioned so that energy absorption and release by the first and second spring means respectively during rotation and reciprocation of the pumping plunger is in a substantially out of phase relationship to thereby eli'ect a balancing of the torque load on the drive shalt and thereby eliminate undesirable pulsating torque forces on said drive shalt.

Relerences Cited in the file of this patent UNITED STATES PATENTS 774.034 Brillie Nov. 1, 1904 2.8l0,376 Mdinger Oct. 22, i957 FOREIGN PATENTS 1,039,309 Germany Sept. 18, i958 

1. IN A DRIVE MECHANISM FOR A FUEL INJECTION PUMP HAVING A ROTATABLE AND A RECIPROCATIVE PLUNGER, THE COMBINATION OF A ROTATABLE DRIVE SHAFT CONNECTED TO ROTATE SAID PLUNGER, A FIRST SET OF ROLLERS FIXEDLY MOUNTED WITHIN SAID PUMP, A FIRST CIRCULAR FACE CAM ATTACHED TO ONE END OF SAID PUMPING PLUNGER AND CONTACTING SAID ROLLERS FOR RECIPROCATING THE PLUNGER AS IT ROTATES, A FIRST SPRING CONNECTED TO OPPOSE AXIAL DISPLACEMENT OF SAID PLUNGER IN ONE DIRECTION AND EFFECTIVE TO MOVE THE PLUNGER IN THE OPPOSITE DIRECTION, A SECOND SET OF ROLLERS ALSO FIXEDLY MOUNTED WITHIN SAID PUMP, A SECOND CIRCULAR FACE CAM MOUNTED ON SAID DRIVE SHAFT AND CONTACTING SAID ROLLERS, AND A SECOND SPRING ACTING AGAINST SAID SECOND CAM AND TENDING TO OPPOSE AXIAL DISPLACEMENT OF SAID SECOND CAM AS IT ROTATES, SAID SECOND CAM BEING MOUNTED IN A RELATIONSHIP THAT IS SUBSTANTIALLY OUT OF PHASE WITH SAID FIRST CAM WHEREBY ONE OF SAID SPRINGS IS BEING COMPRESSED WHILE THE OTHER IS BEING RELEASED SO THAT THE DRIVING LOAD ON SAID DRIVE SHAFT IS SUBSTANTIALLY BALANCED. 